This invention relates generally to processes for manufacturing semiconductor integrated circuits and, particularly, to the removal of etch residues and copper oxides from copper lines.
Fluorine-based plasma etching is commonly used to etch photoresist to generate patterns on a semiconductor device. A residue is left behind on the etched wafer that essentially includes constituents of the plasma gas and the material etched. Normally, gases composed of carbon and fluorine are used for plasma etching resulting in a residue made of carbon and fluorine. Further, the residue may be polymerized due to the generation of free radicals and ions in the high-energy plasma environment.
Particularly with photoresists in advanced semiconductor processes, such as the 193 nm photoresist, wherein a fluorine-rich plasma etch is used, and with 157 nm, in which case the photoresist itself being fluorine-based. This residue may include carbon, hydrogen, and fluorine, and is highly chemically inert and is, therefore, relatively difficult to remove with conventional wet chemical etches. The use of delicate interlayer dielectrics, including porous materials, may prevent the use of ashing for residue removal. Conventional wet cleans may not work well with this relatively inert chemical residue. Few liquid solvents can penetrate fluorine-based polymers like teflon, or even the cross-linked and damaged residue and remaining organic stack.
Thus, there is a need for a better way to remove resistant etch residues.